Combination of sliding mode controller and PI controller using fuzzy logic controller

This paper proposes an approach to combine a sliding mode controller (SMC) and a PI controller using a fuzzy logic controller. A SMC can give good transient performance, but the steady state performance is poor due to the presence of discontinuous control which causes chattering. On the other hand, a PI controller can offer zero steady state error. Hence, by combining these two controllers using a fuzzy logic controller one can utilise their advantages and remove the disadvantages. Although the PI sub-system has one order higher than the SMC subsystem, the closed-loop system stability under the control of this fuzzy logic controller can still be proved by applying a new proposed method. An illustrative example shows that good transient and steady state responses can be obtained by applying the proposed controller.